A number of organic synthesis reactions using a transition metal complex as a catalyst have hitherto been developed and made use of for various purposes. In particular, many reports have been made on transition metal catalysts useful for asymmetric synthesis reactions, such as asymmetric hydrogenation and asymmetric isomerization. Among them, complexes in which an optically active tertiary phosphine compound is coordinated to a metallic rhodium are well known for asymmetric hydrogenation. For example, a rhodium-phosphine complex using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as BINAP) as a ligand is disclosed in JP-A-55-61937 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Further, S. Inoue, et al. report that asymmetric hydrogenation of geraniol or nerol in the presence of various rhodium-phosphine complex catalysts gave citronellol having an optical purity of 66% ee.
Also, there are reports on ruthenium complexes, though fewer than on rhodium complexes. For example, known ruthenium complexes include those having BINAP or 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as T-BINAP) as a ligand, i.e., Ru.sub.2 Cl.sub.4 (BINAP).sub.2 NEt.sub.3 or Ru.sub.2 Cl.sub.4 (T-BINAP).sub.2 NEt.sub.3 (wherein Et represents an ethyl group, hereinafter the same) and [RuH.sub.l (R-BINAP).sub.m ]X.sub.n (wherein R represents a hydrogen atom or a methyl group; X represents ClO.sub.4, BF.sub.4, or PF.sub.6 ; l represents 0; or 1; when l is 0, m represents 1, and n represents 2; when l is 1, m represents 2, and n represents 1) as disclosed in a publication. However, these ruthenium complexes have such disadvantageous that the preparation thereof involves complicated procedures or the yield or stability of these complexes are slightly unsatisfactory. Moreover, their catalytic activity and its duration are not deemed sufficient.
Although metallic rhodium provides excellent complex catalysts, it is expensive due to limits in place and quantity of production, so that it forms a relatively large proportion in the production cost, leading to an increased price of final products. To the contrary, metallic ruthenium is cheaper than metallic rhodium and is therefore expected to provide industrially advantageous catalysts. However, ruthenium complexes have unsolved problems with respect to reaction accuracy and applicability. Accordingly, it has been demanded to develop a catalyst which can be prepared with ease and at a low cost, which exhibits high activity for a long duration, and which achieves a high asymmetric yield, i.e., high optical purity of products, in asymmetric reactions.